The human eye, in simple terms, functions to provide vision by transmitting and refracting light through a clear outer portion called the cornea and focusing the image by way of the lens onto the retina at the back of the eye. The quality of the focused image depends on many factors including the size, shape, and length of the eye, and the shape and transparency of the cornea and lens.
When trauma, age, or disease causes the lens to become less transparent, vision deteriorates because of a reduction in light transmitted to the retina. This deficiency in the eye's lens is medically known as a cataract. The treatment for this condition is often surgical removal of the lens and implantation of an artificial lens, typically known as an intraocular lens (IOL).
An IOL is often foldable and inserted into the eye through a relatively small incision by being advanced through an IOL insertion cartridge, which causes the IOL to fold. The IOL is typically advanced through the insertion cartridge by a plunger-like device.
Before inserting an IOL, the old lens is usually removed through a process called phacoemulsification. In phacoemulsification, an eye's lens is emulsified with an ultrasonic handpiece and aspirated from the eye. Aspirated fluids are replaced with an irrigation of balanced salt solution, thus maintaining the anterior chamber, as well as cooling the handpiece. The irrigation fluid and the aspiration suction are usually supplied by a remote surgical console, which is coupled to the handpiece through several feet of tubing.
Typically, a second stage is required to completely remove the lens, as the first stage only extracts the main portions. Thus, after phacoemulsification, an irrigation-aspiration probe is used to aspirate out the remaining peripheral cortical matter, while leaving the posterior capsule intact.